88 SIERRA DE UMANGO 
the west is barren and composed entirely of these sandstone 4 
layers. | 
On his map from 1911 Bodenbender has indicated the exis- 
tence of tertiary strata along the course of the Rio Bermejo south 
from San Isidro (Paso de Isidro). I have, however, on this route 
seen only the above named red sandstone layers, exposed already 
in the described profile of the Paso de Lamar. 
The writer has personelly traversed only the northern part of the 
Pagancillo lowland, between Villa Union and Puerto Alegre. ‘Here 
the road passes over a hilly landscape, composed entirely of soft 
younger strata. While the small meseta hills in the vicinity of the 
Villa Union consist of the red (cretaceous?) sandstone dipping 
gently eastward, the road leads further to the east into the above 
named soft-rock-terrane, known as the Lomas de Villa Union. The 
topography here has the character of „bad land“ and the strata are 
always pale yellowish or orange-coloured and of very soft consis- 
tence. They would probably have been levelled already by the 
erosion, if they did not carry a horizontal covering sheet of hardened 
diluvial gravels. The dip of the strata is constant, about 45° W. 
Conglomerate beds are frequent. The series corresponds to the 
Calchaqui formation. | 
From the Puerto Alegre may be observed (with field glass), that 
the numerous terrace-remnants (high diluvial terraces) on the wes- 
tern slope of the Serrania de Famatina (the cuesta bordering the 
Pagancillo lowland to the east) are composed: of the same soft 
pale-coloured layers as in the Lomas. Here the dip is, according 
to the profiles of Bodenbender (1911), steep toward the west. 
The terrace planes therefore cut obliquely across the edges of the 
strata. 
At Puerto Alegre in the erosion profiles of the dry current bottom 
is seen a series of vertically tilted layers of dark brown sandstone 
and conglomerate. Then follows to the east the red sandstones of 
the ,Paganzo“, disappearing toward the Famatina mountain abrubtly 
